Process for preparing C3-6 (hydro)fluoroalkenes by dehydrohalogenating C3-6 halo(hydro)fluoroalkanes in the presence of a zinc/chromia catalyst
a technology of hydrofluoroalkene and dehydrohalogenation, which is applied in the field of process for preparing (hydro) fluoroalkenes, can solve the problems of toxic and/or expensive reagent handling, low yield, and inability to meet the requirements of the process
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example 1
Dehydrofluorination of 1,1,1-trifluoro-2,3-dichloropropane
[0102]A 2 g sample of an amorphous catalyst composed of 6% Zn by weight on chromia was charged to a 15 cm×1.25 mm Inconnel reaction tube installed inside a tubular furnace. This catalyst was dried at 250° C. for 1 hour then pre-fluorinated at an N2:HF ratio of 6:1 for 1 hour at 250° C. before increasing the temperature to 380° C. at which point the nitrogen diluent flow was stopped. After approximately 18 hours, the HF feed was switched off and the reactor was cooled to 200° C.
[0103]The organic feed (comprising 1,1,1-trifluoro-2,3-dichloropropane) and HF were then passed over the catalyst with a contact time of 5 seconds at a reaction temperature of from 180 to 380° C. (varied at 20° C. intervals) and a pressure of 1 bara using either an HF:organics ratio of 15:1 or 5:1. At each temperature, the system was allowed to equilibrate for about 20 minutes before reactor off-gas samples were taken at each temperature for analysis by...
example 2
Dehydrofluorination of 1,1,1,2,2-pentafluoropropane
[0110]A 2 g sample of an amorphous catalyst composed of 6% Zn by weight on chromia was charged to a 15 cm×1.25 mm Inconel reaction tube installed inside a tubular furnace. This catalyst was dried at 250° C. for 1 hour then pre-fluorinated at an N2:HF ratio of 6:1 for 1 hour at 250° C. before increasing the temperature to 380° C. at which point the nitrogen diluent flow was stopped. After approximately 18 hours, the HF feed was switched off and the reactor was cooled to 200° C.
[0111]The organic feed (comprising 1,1,1,2,2-pentafluoropropane) and HF was then passed over the catalyst with a contact time of 5 seconds at a reaction temperature of from 180 to 380° C. (varied at 20° C. intervals) and a pressure of 1 bara using either an HF:organics ratio of 15:1 or 5:1. At each temperature, the system was allowed to equilibrate for about 20 minutes before reactor off-gas samples were taken at each temperature for analysis by either GC or GC...
example 3
Dehydrofluorination of 1,1,1,2,2,3-hexafluoropropane (HFC-236cb) and 1,1,1,2,3,3-hexafluoropropane (HFC-236ea) with HF
[0113]A 2 g sample of an amorphous catalyst composed of 6% Zn by weight on chromia was charged to a 15 cm×1.25 mm Inconel reaction tube installed inside a tubular furnace. This catalyst was dried at 250° C. for 1 hour then pre-fluorinated at an N2:HF ratio of 6:1 for 1 hour at 250° C. before increasing the temperature to 380° C. at which point the nitrogen diluent flow was stopped. After approximately 18 hours, the HF feed was switched off and the reactor was cooled to 220-240° C.
[0114]Following pre-fluorination, the dehydrofluorination of either HFC-236ea or HFC-236cb was studied as a function of temperature and HF:236 ratio. Feed gas flow rates were chosen so that a contact time of c.a. 5 seconds was achieved between the catalyst and feed mixture. HF:236 ratios were explored in the range 0-10. At each temperature, the system was allowed to equilibrate for about 20 ...
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